COMPRESSIVE STRENGTH OF CONFINED REINFORCED RECYCLED COARSE AGGREGATE CONCRETE COLUMNS

Abstract

This study examines the compressive behavior of confined concrete incorporating recycled coarse aggregate (RCA) and reinforced with spiral stirrups, aiming to assess its structural viability. Thirty-six cylindrical specimens (150 mm diameter × 300 mm height) were prepared with two RCA replacement levels (0% and 30%) and different spiral stirrup spacings (20, 25, 30, 50, and 100 mm). All specimens were tested under monotonic axial compression at 28 days, and experimental results were compared with theoretical predictions based on Mander’s confinement model. The incorporation of 30% RCA led to a moderate reduction in compressive strength, ranging from 2.85% to 9.72% compared to natural aggregate specimens. However, reducing stirrup spacing increased confinement and significantly improved strength and ductility, effectively compensating for the strength loss associated with RCA. Especially, specimens with 30% RCA and a 20 mm stirrup spacing achieved compressive strengths comparable to those of conventional concrete. Mander’s model consistently underestimated the compressive strength of confined RCA concrete, indicating that it provides conservative predictions when RCA is used. These results support the structural application of RCA in reinforced concrete, particularly when adequate confinement is provided.